He was a passenger on EgyptAir flight MS804 - an Airbus A320 with 56 passengers and 10 crew members from Paris to Cairo - which went down about halfway between the Greek island of Crete and Egypt's coastline, or around 175 miles offshore, after take-off from Charles de Gaulle Airport.

The plane spun all the way around and suddenly lost altitude just before vanishing from radar screens around 2.45 am Cairo time (12.45 am GMT).

Egyptian and Russian officials said it may have been brought down by terrorists, and t here are no signs of survivors.

Alastair Osman told ITV News: "Richard has two kids. Richard was a very kind person, loving person, very focused. He was a workaholic and never deviated from the straight path.

"A very admirable person and a lot of people admired him for his strength and values. He's a new dad. A dad for the second time now and I know that would have filled him with love and joy. It's funny how quickly things change."

He told how his brother let him know of the birth of his second child just over three weeks ago.

"Two girls," Mr Osman said. "He texted to tell me I'm an uncle for a second time on April 27."

Egyptian and Greek authorities in ships and planes searched the suspected crash area throughout the day for traces of the airliner or its victims, with more help on the way from the US, Britain and France.

But as night fell, they had yet to find any confirmed debris, at one point dismissing a reported sighting of life vests and other floating material.

Civil aviation minister Sherif Fathi said the disaster was still under investigation but the possibility it was a terror attack "is higher than the possibility of having a technical failure".

Alexander Bortnikov, chief of Russia's top domestic security agency, said: "In all likelihood it was a terror attack."

Asked about why Mr Osman was on the flight, his brother told the news programme: "He would have been going to work I assume. I know he works in both Egypt and another country in Africa.

"I guess it was work related. He's been doing this for years in the gold mining industry. This was a regular trip. He used to do it at least once a month, year after year."

Alastair Osman, who said the family of four were all born in Carmarthen, said: " This is the reality of Isis and groups like that. It's indiscriminate. They don't think any of these people have family members, or a past, or a history of hopes and dreams. It's indiscriminate."

According to the Carmarthen Journal, Mr Osman is 40 and is a former pupil at QE Cambria with family in the Swansea area.

The newspaper said Mr Osman is the son of the late Fekri Osman, a founder of the Werndale private hospital in Bancyfelin.

His father moved to Wales from his native Egypt to work as a consultant in ear, nose and throat surgery in Singleton Hospital, Swansea, it said.

The Journal added that Mr Osman was a qualified geologist and worked for exploration and research companies which involved him travelling widely around the world.

Among those on board were a child and two babies, EgyptAir said. The airline said the 56 passengers included 30 Egyptians, 15 French, two Iraqis and one each from Britain, Sudan, Chad, Portugal, Algeria, Canada, Belgium, Kuwait and Saudi Arabia.

The Airbus A320 was built in 2003 and was flying at 37,000ft, the airline said on Twitter.

It tweeted that the pilot had logged 6,275 flying hours, including 2,101 hours on the A320, and the co-pilot had logged 2,766 hours.

There was confusion over whether a distress signal had been sent by the Airbus A320.

Egypt's civil aviation authority said one was received at 4.26am local time, believed to be an automated message rather than one sent by the pilot.

However the Egyptian military later said it had received no distress message from the aircraft, in a statement on its website.

Meanwhile, French president Francois Hollande held an emergency meeting at the Elysee Palace.

He also spoke with Egyptian president Abdel-Fattah el-Sissi by telephone and agreed to "closely co-operate to establish as soon as possible the circumstances" surrounding the disaster, according to a statement.